1. Field of the Invention
The field of the invention is aqueous polyamide suspensions.
2. Description of the Related Art
Polyamide resins are typically synthesized by reacting dicarboxylic acid-containing compounds with diamine-containing compounds. This reaction produces repeating hydrocarbon subunits connected to each other through amide bond linkages. Nylon is one type of particularly well-known polyamide, although there are many other types of polyamide compounds possessing various strength, flexibility, and solubility properties, due largely to the lengths of the hydrocarbon portions of the reacting species.
One particularly useful type of polyamide is made from polymerized fatty acid, also referred to as dimer acid. These polyamides may be referred to as polymerized fatty acid-based polyamides, or dimer acid-based polyamides. Sometimes these polyamides are also referred to polymerized fatty acid-containing polyamides, however, it should be noted that polymerized fatty acid per se is not present to any great extent in these polyamides, and that the term “polymerized fatty acid-containing” is really a shorthand expression that denotes that the polyamides were prepared from polymerized fatty acid. Regardless of their name, in structural terms these polyamides contain longer hydrocarbon regions than are found in nylons, and may be terminated at each end by organic functional moieties such as amide and ester groups. Generally, the molecular structures of polymerized fatty acid-based polyamides impart to these resins properties of strength and flexibility, making them particularly useful in formulations for protective coatings and gelling agents. Indeed, articles of commerce such as candles, air fresheners, and cable protectants can be manufactured with the use of such resins.
Because of the prominence of the hydrocarbon regions in typical polymerized fatty acid-based polyamides, such resins are often combined with low-polarity components, such as mineral oils and cosmetic-grade esters. However, a few polyamides have been formulated to be compatible with water, as described in the following representative U.S. Patents.
U.S. Pat. No. 5,324,812 discloses preparative procedures and compositions for a water-soluble polyamide resin derived from polyoxyalkylene diamine. This Patent mentioned that the polyamide disclosed therein may be useful in various products including lubricants, mold release agents, disposable items (such as plastic containers), water thickeners, encapsulants, temporary protective coatings, and in particular, hot melt adhesive formulations.
U.S. Pat. No. 5,466,734 discloses preparative procedures and compositions for a cold seal release lacquer comprising polyamide block copolymer, amide wax, alkanolamine, water, and optionally surfactant, wherein the polyamide block copolymer has an acid number of 30-45. Cold seal release lacquers are used as protective coatings for film wrapping of consumable products.
U.S. Pat. Nos. 5,886,135 and 5,948,880 disclose compositions to make dispersions from polyamide, water, and either surfactant or thickener, wherein the surfactant is a mixture of nonionic and anionic surfactants, while the thickener is selected from, e.g., urethane thickeners and polyether thickeners. These Patents disclose preparative procedures wherein an organic phase (comprising organic solvent, polyamide resin, surfactant, and inorganic base) is combined with an aqueous phase (comprising water and acid), after which much of the organic solvent is removed. These polyamides are purportedly useful as coatings and adhesives.
U.S. Pat. No. 5,962,629 discloses a composition for an aqueous dispersion that contains water and polyamide terminated by aminoalkylpiperazyl groups. Related U.S. Pat. No. 5,998,508 discloses a composition for a curable epoxy resin comprising the aqueous dispersion of the '629 Patent in combination with an epoxy resin. Related U.S. Pat. No. 6,013,757 discloses a cord substrate impregnated with the curable epoxy resin of the '508 Patent.
U.S. Pat. No. 6,077,900 discloses a dispersion containing polymerized fatty acid-based polyamide, amide-free polymeric component, and surfactant, and states that this dispersion may be formed by combining the listed components in the presence of water and an organic solvent, where the organic solvent must have some solubility in water. This Patent further discloses that the pH of the organic and aqueous phases needs to be adjusted so as to promote formation of an oil-in-water dispersion when combined, without polyamide coagulation. The '900 Patent also states that these dispersions are useful in various products such as printing inks and general coating material.
U.S. Pat. No. 6,103,809 discloses a composition for an adhesive that contains water-sensitive and/or water-dispersible polyamides. The products may also include wax.
U.S. Pat. No. 6,165,971 discloses an aqueous composition for a cosmetic, comprising a specifically terminated amide-terminated polyamide, and a component selected from surfactant and polyglycoside.
The present invention provides improvements in the art of water-soluble polyamides, and provides other related advantages as disclosed below.